1. Field of the Invention
The present invention relates to a plasma processing apparatus and method.
2. Description of the Related Art
In a manufacturing process of, for example, a semiconductor device or a liquid crystal display device, an etching process for etching a film on a substrate, a film forming process for forming an electrode or an insulating film on the substrate, or the like is performed. Widely employed for the etching or the film forming process is a plasma processing for processing the substrate by using a plasma.
The plasma processing is typically performed in a plasma processing apparatus. As such a plasma processing apparatus, a parallel plate type apparatus having an upper and a lower electrode disposed to face each other in parallel is widely utilized. In the parallel plate type plasma processing apparatus, for example, a plasma is generated in a processing space formed between the lower and the upper electrode by a radio frequency power supplied from a radio frequency power supply in a processing chamber, and a substrate loaded on the lower electrode is processed by the plasma.
Recently, however, in the plasma processing apparatus, the radio frequency power supply is designed to provide a radio frequency of a shorter wavelength to perform, for instance, a higher-density etching process or film forming process. If the radio frequency wave of the shorter wavelength is used, however, the plasma would be concentrated in a central portion of the processing space, resulting in a non-uniform plasma distribution in which the density of the plasma in the central portion of the processing space is higher than that in the peripheral portion thereof. As a result, the plasma processing in a central portion of a wafer progresses faster than that in its peripheral portion, so that final etching results are often found to be non-uniform over the surface of the substrate.
To solve the problem, there has been proposed a plasma processing apparatus having an upper electrode of a substantially convex shape in which its upper central portion protrudes from a peripheral portion thereof (see, e.g., Reference 1). Although, however, this apparatus has aimed at achieving a uniform plasma density in a processing chamber by allowing the plasma to diffuse uniformly throughout the processing chamber, this counterplan has not been effective enough to make an etching rate or a film forming speed be uniform over the whole surface of the substrate sufficiently.    (Reference 1) US Patent Publication No. 2004-0020431    Japanese Patent Laid-open Application No. 2003-297810